Jon Titus provides tips aimed at helping embedded-systems designers save power. Areas covered are peripherals, power sources, memory and more.
Like many inexpensive desktop PCs, my Dell Dimension C521 lacks a serial port. But, don't write off serial communications which will continue to play important roles in industrial controls, point-of-sale terminals and other equipment. USB and Ethernet have a place, but simple serial I/O still solves a lot of problems.
Most likely you know a bit about the Controller Area Network, also called CAN or CAN bus, developed for communications between equipment in vehicles. The CAN has spread into embedded systems, too, but unlike chip-to-chip I2C or SPI connections, CAN communications may occur between cards and systems over a bus that can extend from 10's to 100's of meters. (The ISO-11519 and ISO-11898 standards covers CAN protocols and physical-layer specifications.)
Competitive telecom businesses have realized they can no longer design proprietary hardware. In response to this changed business climate, members of the PICMG, a consortium of industrial-computer vendors, developed PICMG 3.0, or the Advanced Telecom Computing Architecture (ATCA). Marc LeClaire, a product manager in the Advanced Blades and Servers Division at Kontron, stressed that the ATCA standard covers boards, enclosures, interconnections, communications, and other architectural components. "Designers must think of the ATCA as a complete architecture, not simply as a bus."
Years ago I ditched my 9600 bps modem, but I still rely on dial-up modems. Those modems exist in automated teller machines, gasoline pumps, traffic controllers, medical instruments, security systems, point-of-sale (POS) equipment, and other devices. According to several sources, dial-up modems still provide the largest number of access points to the Internet. Fortunately, several OEM vendors supply dial-up modem modules that offer drop-in communications in small packages.
Hi-Tech Software has announced a new compilation technology that generates object code based on call- and pointer-reference graphs derived from all the modules in an embedded program. The new technology, called Omniscient Code Generation (OCG), overcomes problems in conventional compilers that can miss inconsistent calling conventions, variable declarations and redundant code because they compile each module independently and separately. OCG results in more easily ported code that is nearly 50 percent more dense than code from competing compilers.
The Connect ME JumpStart development kit from Digi International includes a Comment ME module and development board. Software provides a 90-day evaluation version of Microsoft's Visual Studio 2005 Professional and the Microsoft .NET Micro Framework SDK plug-in for Visual Studio. This kit provides a quick and easy way to investigate .NET Micro Framework and its related tools and to build an embedded product that requires an Ethernet connection.
On a recent flight I talked with a software-engineering manager about the challenges of finding good embedded-system developers. She told me she has a team of 12 developers, but only three had proficiency with drivers, board-support packages, and boot-loaders. The other nine -- all good application developers -- lacked low-level coding experience. I asked if she had heard of the Microsoft .NET Micro Framework.
"Cost still rules applications," said Ross Bannatyne, Marketing Director at Silicon Laboratories, a supplier of 8051-based MCUs. "If 8-bit MCUs solve problems, why use more expensive 32-bit chips?" Newer 8051 derivatives, for example, execute 100 MIPS and on-chip multiply-accumulate accelerators let them handle signal-processing tasks. According to Bannatyne, some engineers might not realize 32-bit MCUs can incur code penalties. "They might assume an algorithm that requires 16 KB in an 8-bit MCU also needs 16 KB in a 32-bit processor. Often the code takes more memory in the 32-bit processor, often much more."
As a youngster I enjoyed wiring up circuits with knife switches, lamps, buzzers and large dry cells. While in high school I made frequent trips to surplus-electronics stores in New York City and ordered components from mail-order supply houses. My projects included a 4-bit binary adder -- built from switches and relays -- and a tic-tac-toe machine. I also built my share of kits from Knight, Eico and Heath. My friend Bill Kuhn designed and built relay-logic learning machines.
More times than designers might like to admit, they wish for just one more I/O pin on a microcontroller. Three chip-to-chip serial buses can help overcome I/O pin limits. The following information provides a quick overview and points you to sources of more information.
Years ago, designers involved with high-performance computer systems realized the parallel-bus structures found in most computers had run their course. New computer systems, such as those based on VME64x, move data across switched-fabric networks. Unlike a bus that connects all boards to all signals, a switched-fabric network routes communications through switches. Thus communications can take one of several high-speed paths and no longer create a bus bottleneck. In this context, "fabric" implies a point-to-point network that designers can "scale" to accommodate thousands of nodes. But a fabric does not imply the use of a specific hardware or software architecture.
Over the years, I have accumulated articles, books and application notes that relate to sensors and measurement techniques. In this column – a change of pace from ECN's usual Embedded Systems column format – I share many of those resources with you. Some of this information may seem "old," so you may not know about these sources or an Internet search will not find them.
Rotary shaft encoders convert an angular position into an electrical quantity or digital code that a computer can use to determine the location of a connected object. Encoders come in two varieties - absolute and incremental - and most rely on optoelectric or magnetic sensors. Both types divide a 360° rotation into hundred or thousands of equally spaced units, or counts. Thus, engineers can choose an angular resolution that meets their needs. An absolute encoder indicates a specific position within the shaft's 360° rotation and an incremental position indicates the change in rotation from one position to another. (You also can derive velocity and acceleration from encoder signals.)
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